The present invention relates generally to internal combustion engines and, in particular, to a connecting rod and piston used in such an engine.
Internal combustion (IC) engines are in widespread use throughout the world. In a typical IC engine, a rotatable crankshaft is coupled to a reciprocating piston by a connecting rod. The connecting rod transfers power to the crankshaft when fuel is burned in the piston cylinder.
The length of the connecting rod has a significant impact on the performance of the engine. In part this is because the connecting rods in most conventional IC engines do not reciprocate in an exactly linear motion, but instead the motion has an angular component. This angular component results from the lower end of the connecting rod rotating through a path that is concentric to and radially spaced from the crankshaft axis. In other words, when the piston is at mid-stroke, the lower end of the connecting rod is positioned at the side of the crankshaft. In this position, the connecting rod forms an angle relative to the position of the connecting arm when the piston is at top or bottom dead center. Because of this angle, when driving the crankshaft some of the power from combustion is lost due to the force being delivered at the angle and due to any angular deflection of the connecting rod. But by increasing the length of the connecting rod, the angle of the connecting rod at mid-stroke is decreased, and a greater percentage of the available power from the combustion is transmitted to the crankshaft.
Unfortunately, there are physical design constraints on the length of the connecting rod. Most connecting rods have cylindrical bores in their lower and upper ends. The upper end bore is aligned with a cylindrical bore in the piston, and they receive a cylindrical wrist pin to pivotally couple them together. The wrist pin ordinarily needs to be positioned below the piston rings on the piston. This limits the position of the upper end of the connecting arm. Also, the position of the lower end of the connecting rod at the crankshaft is limited by the position of the crankshaft. And just spacing the piston and crankshaft further apart so that a longer connecting rod can be used requires using a bigger engine block, which is often not a satisfactory option due to the increased size and costs of the engine.
Accordingly, it can be seen that a need yet remains in the art for an improved connecting rod and piston arrangement that reduces the angular component of the motion of the connecting rod, thereby increasing the power transmitted to the crankshaft. Furthermore, there remains a need for such a connecting rod and piston arrangement that provides a substantially increased effective length of the connecting rod, thereby reducing the angular component and providing improved power. It is to the provision of such an arrangement that the present invention is primarily directed.
Briefly described, the present invention comprises an internal combustion engine having a crankshaft, a reciprocating piston with a crown, and a connecting rod coupling the crankshaft with the piston. The connecting rod has an upper end coupled to the piston and a lower end coupled to the crankshaft. The lower end can be coupled to the crankshaft by conventional practice.
The upper end is coupled to the piston by a rider that engages and is guided by an arcuate track formed in or on the piston. The arucate track has a center of curvature that defines an upper pivot axis that is above the piston crown. In this way, the connecting rod moves back-and-forth along the arcuate track as it reciprocates with the piston, so that the connecting rod pivots about the upper pivot axis. By pivoting about this axis above the piston crown, the connecting rod has an effective length that is longer that its actual length, and the maximum angle of the connecting rod is reduced relative to those used in known engines. This results in more leverage, therefore, more of the power produced by the combustion in the piston is transferred by the connecting rod to the crankshaft.
In a first exemplary embodiment of the invention, the arcuate track is provided by two (or another number of) arcuate slots in the piston, with the connecting rod upper end positioned between them. Each slot has a lower inner arcuate surface and a generally concentric upper inner arcuate surface. Also, the rider is provided by at least one rider pin with ends that extend from the connecting rod upper end and are received into the arcuate slots. For example, the rider pin can be provided by a bar having a lower arcuate surface and an upper arcuate surface, the surfaces generally concentric with each other and with the slot arcuate surfaces. Additionally, the rider pin can have a hollow shape. Furthermore, the upper end of the connecting rod can have a cavity that receives the rider pin through it so that the rider pin and upper end move together. Other arcuate track and rider arrangements that produce an upper pivot axis above the piston crown for the connecting rod can be suitably employed. Also, other rider pin shapes and structures can be used that permit the rider pin to move back-and-forth along the track.
In a second exemplary embodiment of the invention, the rider pin is solid and thinner between its arcuate surfaces. Also, the rider pin is mounted to a top surface of the connecting rod upper end by conventional fasteners. In this way, the material cost and weight of the rider pin and connecting rod are reduced.
In a third exemplary embodiment of the invention, the rider pin is solid but has a first cavity in its lower arcuate surface that receives the connecting rod end for mounting. The rider pin has a second cavity in one of its ends, and the connecting rod upper end has holes in it that align with the second cavity to receive conventional fasteners. In this way, the connecting rod can be manufactured using standard connecting rod blanks.
An alternative way of stating the invention is that it includes an improvement in an IC engine. The improvement comprises coupling the connecting rod to the piston so that the connecting rod pivots about the upper pivot axis that is above the crown of the piston. For example, the piston can include the arcuate track, and the non-cylindrical rider can be guided along the track and coupled to the connecting rod.
Accordingly, the present invention provides an IC engine with a connecting rod coupled to the piston so that, as it reciprocates with the piston, it pivots about an upper axis point above the piston crown. Thus, the connecting rod has a longer effective length than its actual length because it pivots to a smaller maximum angle than conventional connecting rods. With the connecting rod kept more in-line and deflected less, a greater percentage of the available power from the combustion is transmitted to the crankshaft. This results in a noticeable increase in engine horsepower.